Field
Embodiments of the disclosure generally relate to a pre-heat ring for use in a substrate processing chamber.
Description of the Related Art
Continuous reduction in size of semiconductor devices is dependent upon more precise control of, for instance, the flow and temperature of process gases delivered to a semiconductor process chamber. Typically, in a cross-flow process chamber, a process gas may be delivered to the chamber and directed across the surface of a substrate to be processed. The temperature of the process gas may be controlled by, for example, a pre-heat ring, which surrounds the substrate support.
FIG. 1 illustrates a schematic sectional view of a cross-flow process chamber 100. The process chamber 100 has a rotational substrate support 102 disposed within a processing region defined by an upper dome 104, a lower dome 106, and a chamber side wall 108. The process gas(es) supplied from a process gas source 110 is introduced to the upper processing region 112 through a process gas inlet 114. The process gas inlet 114 is configured to direct the process gas in a laminar flow fashion (e.g., a generally radially inward direction as indicated by flow path 116). During processing, a purge gas is also introduced from a purge gas source 122 into the lower processing chamber 126 through a purge gas inlet 124 at a pressure relatively greater than the pressure of the process gases in the upper processing region 112. A portion of the purge gas will flow upwardly to seep between the substrate support 102 and a pre-heat ring 103 and flow into the upper processing region 112. The upward flow of the purge prevents the process gas from flowing into the lower processing chamber 126, thereby minimizing deposition of undesirable reactant products on the lower dome 106 which would negatively diminish the thermal radiation from the lamps positioned below the lower dome 106. The process gas and the purge gas exit the upper processing region 112 through a gas outlet 118 (opposite the process gas inlet 114) coupled to an exhaust 120.
However, it has been observed that the purge gas flowing upwardly into the upper processing region 112 may cause dilution of the concentration of the process gas near the edge of the substrate 128. The dilution is mainly created near the edge of the substrate 128 which forms turbulence and additional resistance of flow (indicated as region “A”) through which the process gas has to diffuse to travel to the surface of the substrate 128. Therefore, the deposition efficiency at the edge of the substrate is suffered. While rotating the substrate during deposition can create a rotationally symmetric deposition, the uniformity of the film, especially near the edge of the substrate 128, is reduced due to the poor deposition efficiency caused by the dilution. As a result, the film thickness near the edge of the substrate is decreased (edge roll-off effect).
Since flow characteristics directly impact the film uniformity on the substrate, there is a need for an improved deposition apparatus which reduces or eliminates dilution of process gas near the edge of the substrate and prevents the process gas from entering into the lower processing region of the process chamber during processing.